Plain-language explanation.
Computer networks connect computers together so they can share data. The internet is the world's largest computer network. Networks work by breaking data into packets, sending them through routers and switches, and reassembling them at the destination — like parcels in a postal system.
Core concepts and standard treatment.
Core networking covers the OSI model (7 layers: physical — cables, signals; data link — Ethernet, MAC addresses; network — IP addressing, routing; transport — TCP/UDP; session; presentation — TLS; application — HTTP, DNS) and the simpler TCP/IP model (4 layers: network access, internet, transport, application). Key protocols: IP addressing (IPv4 — 32-bit dotted decimal; CIDR — Classless Inter-Domain Routing; subnetting; IPv6 — 128-bit — adoption challenges), TCP vs UDP (TCP — reliable, ordered, connection-oriented — 3-way handshake — SYN/SYN-ACK/ACK; UDP — fast, unreliable, connectionless — DNS, video streaming, gaming), HTTP/HTTPS (request-response; methods — GET, POST, PUT, DELETE, PATCH; status codes — 2xx, 3xx, 4xx, 5xx; HTTP/2 — multiplexing, header compression; HTTP/3 — QUIC over UDP), and DNS (domain resolution — recursive vs authoritative; TTL; DNSSEC; DNS-over-HTTPS — DoH).
Deeper theory, debates and edge cases.
Advanced networking covers routing protocols (distance vector — RIP; link-state — OSPF, IS-IS — Dijkstra; BGP — Border Gateway Protocol — the 'protocol of the internet' — autonomous systems — AS — BGP hijacking; MPLS — label switching), software-defined networking (SDN — control plane separation — OpenFlow; network function virtualisation — NFV; SD-WAN; intent-based networking — Cisco DNA), network security (firewall — stateful inspection; IDS/IPS; DDoS mitigation — anycast scrubbing — Cloudflare; zero trust network access — ZTNA — BeyondCorp; VPN — IPSec, WireGuard; network segmentation — VLANs; micro-segmentation), and performance engineering (queuing theory — M/M/1 queue — Little's Law — L = λW; congestion control — TCP cubic, BBR — Bottleneck Bandwidth and Round-Trip time — Google QUIC; CDN architecture — PoP — Point of Presence; anycast routing; network peering — IXP — Internet Exchange Points).
How it is applied in practice.
At the network architect, site reliability engineer, and cloud infrastructure engineer level, practitioners hold CCIE / JNCIE / AWS networking certifications; design large-scale network infrastructure (Google's Jupiter fabric — 5-petabit network; Azure ExpressRoute / AWS Direct Connect — dedicated private connectivity; submarine cable systems — TeleGeography; 5G network slicing — NFV in mobile core); contribute to IETF RFC standards (QUIC — RFC 9000; HTTP/3 — RFC 9114; WireGuard — RFC pending; DPDK — Data Plane Development Kit for kernel-bypass networking); implement observability for network performance (eBPF-based network monitoring — Cilium, Pixie; distributed tracing — Jaeger, Zipkin; Prometheus + Grafana for network telemetry; SFlow / NetFlow / IPFIX for traffic analysis); and advise on network security compliance (PCI-DSS network segmentation; NIST SP 800-53 network security controls; SASE — Secure Access Service Edge — Gartner).